1. Field of the Invention
This invention generally relates a stent. More specifically, the present invention relates to a stent comprising a tubular flexible body having a wall formed by a web structure and having a radiopaque portion.
2. Background Information
Very different types of stents are already known from the prior art. Stents form a vascular prosthesis made from a physically compatible material. The stent is used for expanding blood vessels or also other body orifices and for keeping the vessels in their expanded state. To this end, the stent is positioned in a patient's body in its non-expanded state and is then expanded by suitable means, i.e. a balloon catheter. During expansion the individual web portions of the stent are deformed such that the stent permanently remains in its expanded form.
For a better localization of the stent in the patient's body the stents are made of metal or stainless steel or the like. Nowadays the stents become thinner so that even the metallic stents can not be localized. Therefore, some stents are covered with a radiopaque coating. The U.S. Pat. No. 5,607,442 discloses a stent that is plated with a high densitiy radiopaque metal such as gold or tantalum. The teaching of this patent shows a stent which is plated to a sufficient thickness on its longitudinal wires to make it clearly radiopaque in fluroscopy. This has the advantage, that the stent can clearly be viewed. On the other hand, the metallic stent plated with a radiopaque metal has the disadvantage that, if the boundary surface between the two materials comes into contact with blood or another water-containing fluid the stent may be corrupted by electrolytic corrosion. Furthermore, the coating of the stent with materials like gold is relatively expensive.
Another possible solution is to attach a portion containing the radiopaque material to the web structure. In this case, there is an area where the two materials are in contact together. Normally, both materials are made of metal. If blood flowing through the vessel comes into contact with the two different metals, electrolytic corrosion will occur which will lead to a damage of the stent and/or to an irritation of the vessel.
With regard to the state of the art there is a strong demand for creating a stent with a thin surface and which is sufficiently radiopaque so that it can be visualized under fluroscopy without the disadvantage of electrolytic corrosion.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved stent. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.